

    //////////////////////////////////////////////////////  
    // file_client.c  socket传输文件的client端示例程序   
    // ///////////////////////////////////////////////////  
    #include<netinet/in.h>                         // for sockaddr_in  
    #include<sys/types.h>                          // for socket  
    #include<sys/socket.h>                         // for socket  
    #include<stdio.h>                              // for printf  
    #include<stdlib.h>                             // for exit  
    #include<string.h>                             // for bzero  
      
    #define HELLO_WORLD_SERVER_PORT       6666  
    #define BUFFER_SIZE                   1024  
    #define FILE_NAME_MAX_SIZE            512  

    int main(int argc, char **argv)  
    {  
        if (argc != 2)  
        {  
            printf("Usage: ./%s ServerIPAddress\n", argv[0]);  
            exit(1);  
        }  
      
        // 设置一个socket地址结构client_addr, 代表客户机的internet地址和端口  
        struct sockaddr_in client_addr;  
        bzero(&client_addr, sizeof(client_addr));  
        client_addr.sin_family = AF_INET; // internet协议族  
        client_addr.sin_addr.s_addr = htons(INADDR_ANY); // INADDR_ANY表示自动获取本机地址  
        client_addr.sin_port = htons(0); // auto allocated, 让系统自动分配一个空闲端口  
      
        // 创建用于internet的流协议(TCP)类型socket，用client_socket代表客户端socket  
        int client_socket = socket(AF_INET, SOCK_STREAM, 0);  
        if (client_socket < 0)  
        {  
            printf("Create Socket Failed!\n");  
            exit(1);  
        }  
      
        // 把客户端的socket和客户端的socket地址结构绑定   
        if (bind(client_socket, (struct sockaddr*)&client_addr, sizeof(client_addr)))  
        {  
            printf("Client Bind Port Failed!\n");  
            exit(1);  
        }  
      
        // 设置一个socket地址结构server_addr,代表服务器的internet地址和端口  
        struct sockaddr_in  server_addr;  
        bzero(&server_addr, sizeof(server_addr));  
        server_addr.sin_family = AF_INET;  
      
        // 服务器的IP地址来自程序的参数   
        if (inet_aton(argv[1], &server_addr.sin_addr) == 0)  
        {  
            printf("Server IP Address Error!\n");  
            exit(1);  
        }  
      
        server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);  
        socklen_t server_addr_length = sizeof(server_addr);  
      
        // 向服务器发起连接请求，连接成功后client_socket代表客户端和服务器端的一个socket连接  
        if (connect(client_socket, (struct sockaddr*)&server_addr, server_addr_length) < 0)  
        {  
            printf("Can Not Connect To %s!\n", argv[1]);  
            exit(1);  
        }  
      
        char file_name[FILE_NAME_MAX_SIZE + 1];  
        bzero(file_name, sizeof(file_name));  
        printf("Please Input File Name On Server.\t");  
        scanf("%s", file_name);  
      
        char buffer[BUFFER_SIZE];  
        bzero(buffer, sizeof(buffer));  
        strncpy(buffer, file_name, strlen(file_name) > BUFFER_SIZE ? BUFFER_SIZE : strlen(file_name));  
        // 向服务器发送buffer中的数据，此时buffer中存放的是客户端需要接收的文件的名字  
        send(client_socket, buffer, BUFFER_SIZE, 0);  
      
        FILE *fp = fopen(file_name, "w");  
        if (fp == NULL)  
        {  
            printf("File:\t%s Can Not Open To Write!\n", file_name);  
            exit(1);  
        }  
      
        // 从服务器端接收数据到buffer中   
        bzero(buffer, sizeof(buffer));  
        int length = 0;  
        while(length = recv(client_socket, buffer, BUFFER_SIZE, 0))  
        {  
            if (length < 0)  
            {  
                printf("Recieve Data From Server %s Failed!\n", argv[1]);  
                break;  
            }  
      
            int write_length = fwrite(buffer, sizeof(char), length, fp);  
            if (write_length < length)  
            {  
                printf("File:\t%s Write Failed!\n", file_name);  
                break;  
            }  
            bzero(buffer, BUFFER_SIZE);  
        }  
      
        printf("Recieve File:\t %s From Server[%s] Finished!\n", file_name, argv[1]);  

      
        // 传输完毕，关闭socket   
        fclose(fp);  
        close(client_socket);  
        return 0;  
      
    }  

